A shoe usually includes an upper part protecting the top of a foot and an ankle, a midsole bonded to the bottom of the upper part and made of resin foam material having buffering and elastic properties to disperse and support the weight of a human body when walking, and an outsole bonded to the bottom of the midsole and made of rubber or other material to give a friction force against the ground when walking.
In conventional methods of manufacturing a shoe, an outsole, a midsole, and an upper part are separately produced, then undergo cleaning or pretreatment and bonding sequentially, and are then manually joined together by a worker. Thereafter, they are compressed using a compressor and cooled down, and a complete shoe is obtained after threading and inspection.
Accordingly, at least five skilled workers are required at a minimum of one production line while primer processing and dry, adhesive application, bonding, etc are being performed on each of the outsole, the midsole, and the upper part.
Since the conventional shoe manufacturing methods require drying, compression, cooling, etc. in each of a series of processes such as cleaning, pretreatment, adhesive application, etc. and depend a lot on workers' manual labor, the quality may not be uniform.
In addition, a lot of organic solvent is usually contained in a primer or an adhesive processed during the manufacture of a shoe, and therefore, workers may be exposed to a harmful environment. Moreover, environmental pollution may be caused since harmful solvent is volatilized and released via an application line and a drying process. Furthermore, the burden of personnel expenses causes shoes to be manufactured in developing countries where labor is cheap and environmental regulations are loose.